Specific Process Knowledge/Characterization/Stress measurement

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Stress measurements of a thin film can be measured by measuring the wafer bow before and after deposition of a thin film. If the then film is deposited on both sides of the wafer, you can measure the bow after deposition and again after removing the film from one of the sides.

The procedure is as follows:

When the deposition is on one side of the wafer

1. Make a pre-stress measurement. Measure the wafer bow on one of the stylus profilometers (Dektak XTA_new or Dektak 8). Save the measurement. It is a good idea to measure across most of the wafer (at least along 70% of the wafer diameter) in two directions perpendicular to each other.
2. Measure the thickness of the wafer
3. Deposit the thin film
4. Measure the thickness of the thin film (ex. using the FilmTek or the Ellipsometer).
5. Make a post-stress measurement. Measure the wafer bow again:
   • On the same profilometer as used for the pre-measurement.
   • With the same recipe as used for the pre-mesurement.
   • On the same position(s) on the wafer as the pre-measurement.
6. Use the program for stress measurement in the profilometer software. Use both the pre-stress measurement and the post-stress measurement.
   • The profiler program asks for a substrate elasticity (choose the substrate type, e.g. Si(100)), substrate thickness, film thickness and the name of the pre-stress measurement.

When the deposition is on both sides of the wafer

1. Deposite the thin film
2. Pre-measurement: Measure the wafer bow on one of the profilometers (Dektak XTA_new or Dektak 8). Save the measurement. It is a good idea to measure across most of the wafer (at least along 70% of the wafer length) in two directions perpendicular to each other.
3. Remove the thin film from one side of the wafer. If it is a single side polished wafer, remove it on the non-polished side.
4. Measure the wafer bow again:
   • On the same profilometer as used for the pre-measurement.
   • With the same recipe as used for the pre-mesurement.
   • On the same position/positions on the wafer as the pre-measurement .
5. Measure the thickness of the substrate
6. Measure the thickness of the thin film (ex. using the FilmTek or the Ellipsometer is possible).
7. Use the program for stress measurement in the profilometer software on the profilometer you used for the measurements. Use both the pre-stress measurement and the post-stress measurement.
   • The dektak program asks for substrate elasticity (choose the substrate type for example Si(111)), substrate thickness, film thickness and the name of the pre-stress measurement.